Overexpression of CXCR4 enhances MTLn3 motility within the primary tumor. GFP labeled MTLn3 transductants were orthotopically injected in the fourth mammary fat pad of SCID mice. Primary tumors with an average volume of 1,300 mm3 were imaged using multiphoton microscopy. (a) Quantitation of the motility events observed in each tumor type. The average number of motile cancer cells (GFP positive) in a 50 μm Z-stack time-lapse series per movie is reported. Six MTLn3 JP animals were imaged with a total of 20 movies analyzed, four MTLn3 CXCR4 animals were imaged with 17 movies analyzed, four MTLn3 CXCR7 and four MTLn3 CXCR4-CXCR7 animals were imaged with 13 and 14 movies analyzed respectively. Means and SEMs are shown. MTLn3 JP vs. MTLn3 CXCR4 (a) P < 0.005; MTLn3 JP vs. MTLn3 CXCR4-CXCR7 (b) P < 0.05 with P values determined using Mann-Whitney. Scale bar: 10 μm. (b) Representative images of the motility observed in the indicated tumors, GFP tumor cells appear as green cells, host cells as dark shadows and ECM in purple. Individual frames are 10 minutes apart. Motile cancer cells are indicated by arrowheads.